It is well established in the prior art that the introduction of steam into the flow path of a gas turbine engine at desired axial locations thereof will increase performance and reduce emissions. Steam injection increases the mass flow and therefore increases the power output. Furthermore, steam injection ahead of the combustion reaction zone reduces the amount of oxides of nitrogen generated in the combustion process. Steam injection is particularly applicable to marine and industrial gas turbine engines which are often located in environments where steam is readily available. Furthermore, the weight of water and steam generating equipment is not the concern it would be with aircraft engines.
Prior art marine and industrial gas turbine engines have been manufactured with an annular bleed air manifold within and constituting a part of the combustion chamber casing. The annular manifold is located at the forward end of the combustion chamber casing. An example of such a gas turbine engine is manufactured by the General Electric Company of Cincinnati, Ohio, under the designation LM 1600. The annular manifold has an exterior port formed in the combustion air casing and a plurality of holes, evenly spaced about the manifold, and leading to the interior of the combustion chamber casing. Such a manifold would constitute a primary introduction point for steam. A steam line from a source of steam could be connected to the port of the manifold and the manifold holes would enable introduction of the steam into the combustion chamber.
A problem arises from the fact that the relatively cool steam from the steam line would impinge upon the already hot wall of the annular manifold, which constitutes a part of the combustion chamber casing. Such impingement would likely result in low cycle fatigue cracking of the combustion chamber casing.
The present invention is directed to a steam deflector assembly mountable about the exterior of the port and within the annular manifold to prevent low cycle fatigue of the combustion chamber casing, thereby avoiding potential cost and time of engine tear-down/rebuild. In addition to protecting the combustion chamber casing from direct impingement of the steam, the steam deflector assembly of the present invention redirects the steam flow from the steam line to assure proper distribution of the steam flow about the annular manifold.